A mobile network architecture of the existing WiMAX (Worldwide Interoperability for Microwave Access) is illustrated in FIG. 1. The architecture comprises a terminal CPEs (Customer Premises Equipment) 101 of the WiMAX, BSs (Base Station) 102 of a WiMAX access network, ASN-GWs (Access Service Network GateWay, access network for short) 104, and PDNs (Packet Data Network) or SDHs (Synchronous Digital Hierarchy) 105. The CPE 101, BS 102 and ASN-GW 103 form an ASN (Access Service Network) of the WiMAX. In regard to interconnection, standard R1 interface is used between the CPE 101 and BS 102, standard R6 interface is used between the BS 102 and ASN-GW 103, standard R8 interface is used between several BSs 102, standard R4 interface is used between several ASN-GWs 103, R3 interface is used between the ASN-GW 103 and CSN 104, and the PDN/SDH 105 is a transmission bearing network of the WiMAX.
Since current main frequency bands of wireless frequencies of a WiMAX system are 2.3/2.5/3.5 GHz, if the conventional integrated macro base station outdoor-covering-indoor method is used, penetration loss, which is generally 18-25 dB in budget, is larger in dense urban area. Thus, using simply the outdoor-covering-indoor method will lead to the reduced outdoor covering radius and the increased number of outdoor stations, thereby increasing network construction cost and augmenting difficulty of rapid network layout. Moreover, traffic-concentrated hotspots, enterprises and business buildings have relatively high requirement for capacity and need high signal to noise ratio in coverage areas so as to be able to satisfy requirement for high-order modulation, such as 16QAM or even 64QAM. The conventional outdoor macro base station and micro base station method cannot satisfy such requirement.
In sum, for the WiMAX and subsequent 4G networking, it is recommended to use a Pico Cell scheme to supplement indoor coverage in cities and dense urban areas. The existing Pico Cell scheme further comprises a baseband pool+Pico RRU method and an integrated Pico base station method. The present invention lays emphasis on an integrated Pico BS-based improvement scheme and device management discussion.
Nowadays, mobile systems usually use the following schemes to deploy access points.
Scheme 1: a number of access points with stand-alone configuration, i.e., Pico BSs, are used in coverage areas; the access points are connected to an access gateway in a central computer room through a transmission network. This scheme is an illustration of an indoor coverage network based on the conventional Pico BS architecture.
The network architecture of this scheme is shown in FIG. 2, in which a Pico BS 201 is deployed in each coverage area (a certain area in a floor as shown in FIG. 2); a number of access points with stand-alone configuration, i.e., Pico BSs 201, are connected through an aggregated switch or router 202; the switch or router 202 provides a R6 interface to a transmission network PDN/SDH 203. Each Pico BS 201 needs to configure a GPS module in order to solve the problem of TDD (Time Division Duplex) system synchronization and prevent system networking interference. The access pints in an area are adjacent in physical locations, however, there is no logic channel communication between them, that is, there is no local access management unit in the whole building or a group of buildings, the communication between the Pico BSs 201, including switching control information among the base stations and user interface information interaction between the access points in the area must be routed to an ASN-GW 204 of a central computer room node via the PDN/SDH 203, and be connected to a CSN 205, and then be processed and sent to a target base station, which is an great waste for bandwidth of the SDH/PDH network. At the same time, due to performance deterioration, such as delay and jitter, caused by public network routing, user experience is degraded significantly. In business buildings and CBD (Center Business District) with medium and large capacity, handover usually occurs in overlapping coverage areas, such as areas between floors, areas between floors and elevators, and aisles. Moreover, requirement for handover is relatively frequent. In the traditional Pico BS architecture, the Pico BS needs to support interfaces, such as twisted pair, optical fiber or coaxial cable, thus GPS antennas are required to be configured to solve the problem of synchronization, which brings relatively large difficulty for indoor deployment, goes against network performance optimization, and does not solve a lot of scenarios or causes heavy cost.
Scheme 2: a Pico/Micro/Pico BS is used to provide a signal source in a coverage area, and RF signals are assigned to a plurality of antenna units through a passive distributed system, power of each antenna unit being equivalent to power of an access point. This scheme is an illustration of is an indoor coverage network based on a signal source base station+passive distributed antenna system architecture and is suitable for small scale indoor coverage networks.
The network configuration of this scheme is shown in FIG. 3, in which a Signal Source BS 301 may be a Micro BS or a Pico BS, depending on indoor coverage scale and network topology. The Signal Source BS provides RF (Radio Frequency) signal to a Power Dividor 302 and a Coupler 303. With layer-by-layer assignment, signals are output to a ceiling mount antenna 304 and a wall mount antenna 305. Type selection of specific antennas is determined by indoor terrain and network planning. The difference between the Power Dividor 302 and the Coupler 303 is that the Power Dividor 302 equally divides power, while the coupler 303 is able to assign power at different ratios to different ports. Using the Pico/Micro/Pico BS to provide the signal source, RF signals are assigned to the plurality of antenna units through the passive distributed system, and the power of each antenna unit equals to the power of the access point. The disadvantage of this scheme is that the Signal Source BS is required to provide relatively large power, the passive distributed system is not suitable for medium and large scale indoor coverage system networking due to its large transmission loss, and cell capacity expansion needs larger workload of engineering construction and deployment.
Scheme 3: a Pico/Micro/Pico BS (shown as 401) is used to provide a signal source in a coverage area, and RF signals are assigned to a plurality of antenna units through an active distributed system, power of each antenna unit being equivalent to power of an access point. This scheme is an illustration an indoor coverage network based on a source base station+active distributed antenna system architecture and is suitable for large scale indoor coverage network.
The network configuration of this scheme is shown in FIG. 4, in which functions connection modes of a Signal Source BS 401, a Power Dividor 402, a Coupler 403, a ceiling mount antenna 404 and a wall mount antenna 405 are the same as those of the indoor coverage network of the passive antenna system architecture shown in FIG. 3. The difference between the active distributed system shown in FIG. 4 and the passive distributed system is that a trunk amplifier 404 is deployed at a position of middle trunk where signal attenuation is relatively large to compensate for the loss caused by line transmission. Since 802.16e is a TDD system, it has strict requirement for time synchronization, and the trunk amplifier 404 is able to extract a transmitting and receiving sequence synchronization signal to compensate for symbol transmitting and receiving sequence caused by different line delays. Using the Pico/Micro/Pico BS to provide the signal source, RF signals are assigned to the plurality of antenna units through the active distributed system, and the power of each antenna unit equals to the power of the access point. This scheme needs to add the trunk amplifier 404 in the middle of transmission line to compensate for line loss and is suitable to medium and large scale indoor coverage networks. However, its disadvantage is that it goes against subsequent capacity expansion, and the TDD system needs to solve the problem of coexistence with the existing systems and the increased cost caused by the introduction of middle nodes. Furthermore, both the cost and workload of maintenance and capacity expansion are relatively large, thereby bringing related problems, such as system reliability.
Although the above description takes a Wimax system as an example, other existing wireless access systems and methods of indoor coverage scenarios or indoor-outdoor combined coverage scenarios also have the following disadvantages.
1) Requirement for indoor cable resource is higher, distributed systems, such as sufficient optical fibers, twisted pairs or coaxial cables, are required; some operators (overseas operators of emerging markets) do not have optical fiber resources or twisted pair resources in most buildings, thus it is very difficult to accelerate networking and decrease deployment cost;
2) In view of the particularity of the TDD system, some operators having 2G/3G indoor coverage need to modify significantly indoor antennas and filters in order to share available distributed systems, thus engineering quantity is enormous, network services have to be interrupted during the modification, and smooth network upgrade cannot be achieved;
3) The deployment of the newly established stand-alone indoor distribution project is relatively difficult and the existing space structure is also needed to be modified, which makes project coordination difficult;
4) With a Pico BS configuring GPS method, if a number of Pico BSs are deployed in medium and large scale indoor coverage scenarios, installation engineering quantity will be huge and maintenance cost will be very high;
5) There are problems of management and local maintenance, as well as switching performance deterioration in individual Pico BS access points;
6) Information interaction between the individual Pico BS access points would decrease transmission efficiency;
7) The individual Pico BS access points will introduce problems of performance bottleneck and expansion in the centralized network management during performance statistics or version upgrade; and
8) There are problems of capacity expansion, scale and performance in the indoor distributed system.